In a known electric power system, as shown in FIG. 9, “radial system,” in which a large-scale power plant 91 is a top and demanders 92 are a base, is fundamental. In FIG. 9, in order to ensure a plurality of transmission systems, a “loop system” is introduced in some part. This kind of electric power system is configured, as a single system, in a broad area (for example, several tens of thousands km2) and large scale (several tens GW).
On the other hand, in recent years, a distributed power generation system of a system collaborative type (for example, refer to Patent Document 1) with solar generation and a fuel cell has been focused. The distributed power generation system of the system collaborative type is usually built in an end region or a local region near the end of the known radiated electric power system, and is premised on interconnection with the electric power system.    Patent document 1: Japanese Patent Application Laid-Open No. 6-327146